When preparing the flight or a diversion, the crew enters its flight plan on a dedicated computer: the FMS (Flight Management System).
FIG. 1 shows the different components of an FMS having functions as listed below and described in the standard ARINC 702 (Advanced Flight Management Computer System, December 1996): they normally provide all or some of the functions of:                Navigation (LOCNAV), 170, for carrying out the optimum location of the aircraft as a function of geographic location means (GPS, GALILEO, VHF radio beacons, inertial systems);        Flight plan (FPLN), 110, for entering the geographic elements forming the skeleton of the route to be followed (departure and arrival procedures, waypoints, airways);        Navigation database (NAVDB), 130, for constructing geographic routes and procedures on the basis of data included in the bases (points, beacons, intercept or altitude legs, etc.);        Performance database (PRF DB) 150, containing the aerodynamic and engine parameters of the aircraft.        Lateral trajectory (TRAJ), 120: for constructing a continuous trajectory on the basis of the flight plan, complying with the required navigation performance and confinement constraints of the aircraft (RNP);        Predictions (PRED), 140: for constructing an optimized vertical profile on the lateral trajectory;        Guidance (GUID), 200, for guiding the aircraft in the lateral and vertical planes on its 3D trajectory, whilst optimizing the speed;        Digital data link (DATALINK), 180 for communicating with control centers and other aircraft.        
A flight plan is formed of “legs” in the AEEC ARINC 424 format. A leg is constituted of an end (which can be a “waypoint”, an end altitude, an intercept with another leg, a beacon radial, a distance with respect to a beacon) and a routing means for arriving at the end.
The lateral trajectory is calculated by the FMS from the flight plan defined by the pilot. On this lateral trajectory, the FMS optimizes (in altitude and speed) a vertical trajectory, complying with possible altitude, speed and time constraints.
A flight plan is generated on the basis of procedures stored in the navigation database 130, structured according to the aforesaid ARINC 424 standard. These procedures are constituted by a set of legs. These digital procedures are the result of data provided by states, corresponding to the points and procedures in force in the airspace flown through.
For example, in order to construct a flight plan, the pilot chooses different procedures indexed by a name. The FMS then extracts these procedures from the database and then carries out a chaining of the successive procedures in order to generate the flight plan.
A flight plan can be used by the FMS for calculating trajectories and predictions and for slaving the aircraft. There are several flight plans managed by the FMS. The active flight plan is the flight plan on which the FMS is capable of guiding the aircraft when it is coupled to the automatic pilot. The actual slaving of the aircraft to the active flight plan is obtained by coupling with the automatic pilot. The temporary flight plan is a working copy coming from the active flight plan and replaces the latter when it is activated. There is also a secondary flight plan.
All of the information entered or calculated by the FMS is grouped on display screens such as textual displays, displays called ND (Navigation Display). An example of an ND navigation display is shown in FIG. 2.
On the screen, the aircraft 20 is shown on its lateral trajectory 21 comprising waypoints WPT. The aircraft is situated on a so-called active segment comprising the waypoint GULEN 22 that the aircraft has just passed (called “FROM”) and the next waypoint TOU 23 towards which it is flying (called “TO”).
With regard to the takeoff and landing phases, air traffic management in general and the regulations relating to safety have for a very long time required state organizations and airport authorities to publish takeoff or landing procedures for flights leaving or arriving at aerodromes. These procedures, graphical and textual, have existed for a long time in paper form only. With the arrival of flight management systems the necessity arose to manage electronically all of the takeoff or landing published by the states.
Thus, at present the textual and graphical procedures are provided by the member states of International Civil Aviation Organization to the suppliers of navigation databases and are converted by theses suppliers into series of legs according to the codification rules of the aforesaid ARINC standard. The takeoff and landing procedures, the latter being called approach procedures, encoded in the ARINC 424 standard, are stored in the database 130 and are used by the FMS during a runway approach phase.
When an aircraft is approaching a runway, it frequently happens that the initial encoded approach procedure of the airport in question ends at a point that does not coincide with the runway entry point Pa.
In general, an encoded approach procedure stored in the navigation database 130 ends at an end point (the last point of the approach) of the MAP (Missed Approach Point) type. An end point of the MAP type is characterized by the fact that it is linked with a “Missed Approach” procedure, also stored in the database 130. The missed approach (or go-around) procedure is used with the situation of the aircraft does not allow it to land as initially foreseen. The approach procedure ending in a point of the MAP type and its associated missed approach procedure MA1 are loaded in the flight plan de the aircraft.
The active flight plan contains only the procedure up to the MAP and therefore only the FMS trajectory coming from that flight plan. On sequencing (overflying) this MAP, the “Missed Approach” flight section is automatically activated in order to allow, if needed, the aircraft to be guided over the missed approach procedure.
A major disadvantage is that, when the end point of the MAP type does not correspond with the runway threshold, the crew has to manage the end of the approach manually in order to join the runway from the end point. It is therefore a critical phase for the crew.
In daytime, the final approach can be carried out visually, on the basis of a published map such as the one shown in FIG. 3.
The point 30 of the MAP type corresponds to the end of the encoded approach procedure loaded in the FMS. The curve in dotted line MA1 corresponds to the missed approach procedure MA1 associated with the approach procedure ending at the point 30.
The curve shown in arrows 31 corresponds to the visual approach procedure that the pilot has to follow manually until reaching the threshold Pa of the runway P. The threshold Pa of the runway is also a point of the MAP type. The curve MA2 shown in dotted line corresponds to the missed approach procedure (or go-around procedure) associated with the visual approach procedure leading to the point Pa.
The problem to be solved is management of these two sections.
At night or in the case of fog, the approach can be carried out with instruments as far as the MAP 30 using a published map such as the one shown in FIG. 4. Starting from the MAP 30, the aircraft can be guided by a radio approach beacon (such as for example in the prior art by an ILS (Instrument Landing System)), possibly managed by the control radar of the airport for the alignment with the runway axis.
It is possible for air companies to add proprietary data in the navigation database 130.
For example, when the initial approach procedure does not end at the runway threshold, some companies, in order to assist their crews, complete the trajectory between the first point and the runway P by encoding a section in the database 130. This encoding is of course carried out on a case by case basis, with the agreement of the air control authorities for the approach to the airport in question.
Thus, additional approach procedures are generated by the air companies and stored in the navigation database 130. The additional procedures have a first point that does or does not coincide with the end point of the MAP type of the initial approach procedure and a last point equal to the runway threshold Pa. The point Pa is linked to a missed approach procedure MA2, also encoded by the company, for the case in which the aircraft finds itself in a situation where it is obliged to go around rather than to land.
The initial approach procedure ending at the MAP is loaded in the flight plan. A major disadvantage is that the present-day systems do not make it possible to have a continuity of the flight plan (and therefore of the reference trajectory) allowing the aircraft to be guided continuously according to the initial approach procedure ending at the MAP (which is not the threshold of the runway) and then according to the additional company procedure up to the runway.
In fact, present-day implementations do not make it possible to have 2 points of the MAP type in the same flight plan: the first MAP point is on the one hand the end of the activated part of the primary flight plan (initial approach procedure) and the start of the associated “Missed Approach” part MA1. It is necessarily unique since, in the prior art, only one single part of the “Missed Approach” type can exist in a portion of flight plan. Thus, in the implementations according to the prior art, the loading of the additional procedure and the associated “Missed Approach” MA2 causes the erasure (by replacement) of the initially entered procedure.
The present-day implementations do not make it possible to link divergent parts of flight plan. However, there is divergence from the initial approach at the point MAP since the flight plan can be followed either towards the additional procedure or towards the “Missed Approach” part MA1 of the initial procedure.
In order to partially overcome this disadvantage, when the initial approach procedure is loaded in an activated primary flight plan, it is possible to load the additional company procedure in another flight plan, for example the secondary flight plan. When the two flight plans, primary and secondary, can be displayed simultaneously, the pilot can then end his approach manually using the secondary flight plan starting from the point MAP of the initial approach. However, there are rules which prohibit the activation of the secondary flight plan. This activation necessitates a series of complex operations by the pilot during the critical phase of the landing, which cannot be done in practice.
Thus, there is no guidance by the FMS in this case, either laterally or vertically, since the activated primary flight plan is no longer being followed.
Moreover, if an event makes it necessary to activate the missed approach procedure and the aircraft has already flown over the MAP of the initial procedure, it is the missed approach procedure MA1 associated with the initial approach that would be activated and not the one corresponding to the additional procedure which is not integrated in the active flight plan.